After you have completed the steps on the Fiance Visa Process on http://usvisas.state.gov,  including paying the necessary fees and submitting the required immigrant visa application form (DS-160) and supporting documents to the National Visa Center (NVC), they will review your file for completeness. Once your case becomes qualified for an interview, NVC will inform you that you are ready to schedule your interview appointment and provide you with a list of the additional documents you will need for the interview at the Embassy.